Backpack



FIG. 1 is a perspective view of a backpack;

FIG. 2 is a perspective, partially exploded view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a front side elevation view thereof;

FIG. 6 is a rear side elevation view thereof;

FIG. 7 is a right side elevation view thereof; and,

FIG. 8 is a left side elevational view thereof.

The broken lines depict portions of the article that form no part of the claimed design. 

CLAIM I claim the ornamental design for a backpack, as shown and described. 